Dust in the Photospheric Environment II. Effect on the Near Infrared Spectra of L and T Dwarfs

We report an attempt to interpret the spectra of L and T dwarfs with the use of the Unified Cloudy Model (UCM). For this purpose, we extend the grid of the UCMs to the cases of log g = 4.5 and 5.5. The dust column density relative to the gas column density in the observable photosphere is larger at the higher gravities, and molecular line intensity is generally smaller at the higher gravities. The overall spectral energy distributions (SEDs) are f_{J} < f_{H} < f_{K} in middle and late L dwarfs, f_{J} f_{K} in early T dwarfs (L/T transition objects), and finally f_{J} > f_{H} > f_{K} in middle and late T dwarfs, where f_{J}, f_{H}, and f_{K} are the peak fluxes at J, H, and K bands, respectively, in f_{nu} unit. This tendency is the opposite to what is expected for the temperature effect, but can be accounted for as the effect of thin dust clouds formed deep in the photosphere together with the effect of the gaseous opacities including H_2 (CIA), H_2O, CH_4, and K I. Although the UCMs are semi-empirical models based on a simple assumption that thin dust clouds form in the region of T_{cr} < T < T_{cond} (T_{cr} = 1800K is an only empirical parameter while T_{cond} about 2000K is fixed by the thermodynamical data), the major observations including the overall SEDs as well as the strengths of the major spectral features are consistently accounted for throughout L and T dwarfs. In view of the formidable complexities of the cloud formation, we hope that our UCM can be of some use as a guide for future modelings of the ultracool dwarfs as well as for interpretation of observed data of L and T dwarfs.Comment: 43 pages, 13 figures, to appear in Astrophys. J. (May 20, 2004) Some minor corrections including the address of our web site, which is now read

Water in Emission in the ISO Spectrum of the Early M Supergiant Star mu Cephei

We report a detection of water in emission in the spectrum of the M2 supergiant atar mu Cep (M2Ia) observed by the Short Wavelength Spectrometer (SWS) aboard Infrared Space Observatory (ISO) and now released as the ISO Archives. The emission first appears in the 6 micron region (nu2 fundamental) and then in the 40 micron region (pure rotation lines) despite the rather strong dust emission. The intensity ratios of the emission features are far from those of the optically thin gaseous emission. Instead, we could reproduce the major observed emission features by an optically thick water sphere of the inner radius about two stellar radii (1300Rsun), Tex = 1500K, and Ncol (H2O) = 3.0E+20/cm2. This model also accounts for the H2O absorption bands in the near infrared (1.4, 1.9, and 2.7 micron) as well. The detection of water in emission provides strong constraints on the nature of water in the early M supergiant stars, and especially its origin in the outer atmosphere is confirmed against other models such as the large convective cell model. We finally confirm that the early M supergiant star is surrounded by a huge optically thick sphere of the warm water vapor, which may be referred to as MOLsphere for simplicity. Thus, the outer atmosphere of M supergiant stars should have a complicated hierarchical and/or hybrid structure with at least three major constituents including the warm MOLsphere (T about 1.0E+3K) together with the previously known hot chromosphere (T about 1.0E+4K) and cool expanding gas-dust envelope (T about 1.0E+2K).Comment: 14 pages, 5 postscript figures, to appear in ApJ

Nonequilibrium Steady State of Photoexcited Correlated Electrons in the Presence of Dissipation

We present a framework to determine nonequilibrium steady states in strongly correlated electron systems in the presence of dissipation. This is demonstrated for a correlated electron (Falicov-Kimball) model attached to a heat bath and irradiated by an intense pump light, for which an exact solution is obtained with the Floquet method combined with the nonequilibrium dynamical mean-field theory. On top of a Drude-like peak indicative of photometallization as observed in recent pump-probe experiments, new nonequilibrium phenomena are predicted to emerge, where the optical conductivity exhibits dip and kink structures around the frequency of the pump light, a midgap absorption arising from photoinduced Floquet subbands, and a negative attenuation (gain) due to a population inversion.Comment: 5 pages, 3 figures, published versio

Spectral Classification and Effective Temperatures of L and T Dwarfs Based of Near-Infrared Spectra

We have obtained near-infrared spectra of L dwarfs, L/T transition objects and T dwarfs using Subaru. Resulting spectra are examined in detail to see their dependence on the spectral types. We have obtained bolometric luminosities of the objects with known parallaxes in our sample, first by integrating the spectra and second by K band bolometric correction. We derive the relation between effective temperature and spectral type.Comment: To appear in May 20, 2004 issue of ApJ There is a companion paper by Tsuji, Nakajima and Yanagisaw

Infrared Spectra and Visibilities as Probes of the Outer Atmospheres of Red Supergiant Stars

In the light of the recent results of the stellar interferometry, we examine the nature of the extra molecular layer outside the photosphere of red super- giant stars, so far studied mostly with the use of the infrared spectra. Although the visibility data are more direct probes of the spatial structure of the outer atmosphere, it is essential that they are analyzed in combination with the spectral data of a wide spectral coverage. In the case of the M2 supergiant mu Cephei, several sets of data, both spectra and visibilities, strongly suggested the presence of an extra-molecular layer, and its basic parameters are estimated to be: excitation temperature T_ex = 1600 K, column densities of CO and H2O N_col = 3.0d+20/cm2, and inner radius R_in = 2.0R*. The result shows reasonable agreement with the one based on the infrared spectra alone, and this may be because the infrared spectra already include some information on the spatial structure of the outer atmosphere. It is important, however, that the model inferred from the spectra is now fully supported with the recent visibility data. In the case of the M2 supergiant alpha Orionis, the infrared spectra and visibilities show a consistent picture in that its molecular layer is closer to the photosphere (R_in = 1.3R*) with higher gas temperature (T_ex = 2250 K) and lower gas column density (N_col = 1.0d+20/cm2), compared with that of mu Cephei. Some controversy on the interpretation of the mid infrared data of alpha Orionis can be reconciled.Comment: 47 pages, 14 Postscript figures, to be published in the Astrophysical Journa

Dust in the Photospheric Environment: Unified Cloudy Models of M, L, and T Dwarfs

We address the problem of how dust forms and how it could be sustained in the static photospheres of cool dwarfs for a long time. In the cool and dense gas, dust forms easily at the condensation temperature, T_cond, and the dust can be in detailed balance with the ambient gas so long as it remains smaller than the critical radius, r_cr. However, dust will grow larger and segregate from the gas when it will be larger than r_cr somewhere at the lower temperature, which we refer to as the critical temperature, T_cr. Then, the large dust grains will precipitate below the photosphere and only the small dust grains in the region of T_cr < T < T_cond can be sustained in the photosphere. Thus a dust cloud is formed. Incorporating the dust cloud, non-grey model photo- spheres in radiative-convective equilibrium are extended to T_eff as low as 800K. Observed colors and spectra of cool dwarfs can consistently be accounted for by a single grid of our cloudy models. This fact in turn can be regarded as supporting evidence for our basic assumption on the cloud formation.Comment: 50 pages with 14 postscript figures, to be published in Astrophys.

High-Resolution Infrared Spectroscopy of the Brown Dwarf Epsilon Indi Ba

We report on the analysis of high-resolution infrared spectra of the newly discovered brown dwarf Epsilon Indi Ba. This is the closest known brown dwarf to the solar system, with a distance of 3.626 pc. Spectra covering the ranges of 2.308-2.317 microns and 1.553-1.559 microns were observed at a spectral resolution of R=50,000 with the Phoenix spectrometer on the Gemini South telescope. The physical paramters of effective temperature and surface gravity are derived by comparison to model spectra calculated from atmospheres computed using unified cloudy models. An accurate projected rotational velocity is also derived.Comment: 9 pages, 3 figures. Astrophysical Journal Letters, in pres

Correlated electron systems periodically driven out of equilibrium: Floquet + DMFT formalism

We propose to combine the Floquet formalism for systems in ac fields with the dynamical mean-field theory to study correlated electron systems periodically driven out of equilibrium by external fields such as intense laser light. This approach has a virtue that we can nonperturbatively include both the correlation effects and nonlinear effects due to the driving field, which is imperative in analyzing recent experiments for photoinduced phase transitions. In solving the problem, we exploit a general theorem that the Hamiltonian in a Floquet matrix form can be exactly diagonalized for single-band noninteracting systems. As a demonstration, we have applied the method to the Falicov-Kimball model in intense ac fields to calculate the spectral function. The result shows that photoinduced midgap states emerge from strong ac fields, triggering an insulator-metal transition.Comment: 19 pages, 12 figures; minor change

Development of periodontal tissue regeneration therapy with new bioactive agents -- studies on brain-derived neurotrophic factor and ameloblastin peptide --

To develop the periodontal regeneration therapy using bioactive agents, effects of two potential agents, brainderived neurotrophic factor (BDNF) and a synthetic peptide of ameloblastin on growth and differentiation of periodontal ligament cells in vitro and tissue healing in vivo. Both agents enhanced proliferation and mineralization of the periodontal ligament cells and induced periodontal tissue regeneration. We showed that BDNF and the ameloblastin peptide could be used as the promising medication to promote periodontal tissue regeneration

Severe progressive scoliosis due to huge subcutaneous cavernous hemangioma: A case report

Cavernous hemangioma consists mainly of congenital vascular malformations present before birth and gradually increasing in size with skeletal growth. A small number of patients with cavernous hemangioma develop scoliosis, and surgical treatment for the scoliosis in such cases has not been reported to date. Here we report a 12-year-old male patient with severe progressive scoliosis due to a huge subcutaneous cavernous hemangioma, who underwent posterior correction and fusion surgery. Upon referral to our department, radiographs revealed a scoliosis of 85° at T6-L1 and a kyphosis of 58° at T4-T10. CT and MR images revealed a huge hemangioma extending from the subcutaneous region to the paraspinal muscles and the retroperitoneal space and invading the spinal canal. Posterior correction and fusion surgery using pedicle screws between T2 and L3 were performed. Massive hemorrhage from the hemangioma occurred during the surgery, with intraoperative blood loss reaching 2800 ml. The scoliosis was corrected to 59°, and the kyphosis to 45° after surgery. Seven hours after surgery, the patient suffered from hypovolemic shock and disseminated intravascular coagulation due to postoperative hemorrhage from the hemangioma. The patient developed sensory and conduction aphasia caused by cerebral hypoxia during the shock on the day of the surgery. At present, two years after the surgery, although the patient has completely recovered from the aphasia. This case illustrates that, in correction surgery for scoliosis due to huge subcutaneous cavernous hemangioma, intraoperative and postoperative intensive care for hemodynamics should be performed, since massive hemorrhage can occur during the postoperative period as well as the intraoperative period